The present invention relates to a power-assisted vehicle transmission and, particularly, to a power-assisted transmission in which the speed of gear shifting may be controlled.
In German Pat. Application Ser. No. DE-OS 27 42 032, there is disclosed a power-assisted transmission, the gear engagement of which is effected by either hydraulic or pneumatic power cylinder actuators. Such arrangements are advantageous, particularly in relatively heavy commercial-type vehicles, where excessive gearshift lever forces would otherwise be required to effect engagement of the gears during shifting.
It has been found that under certain driving conditions, such as in ascending steep grades, the speed at which the power actuators effect the gear shifting is too slow. This results in the vehicle losing excessive speed during the shifting period.
While it is possible to increase the force of shifting to obtain faster response during grade shifting by increasing the size of the power-assist cylinders, or by increasing the actuating pressure, this would result in excessive shifting forces under normal conditions and, accordingly, excessive gear wear, since under normal conditions increased shifting forces to obtain faster gear shifting is unnecessary.